Channel letters are used to provide signage for buildings, shopping malls, and the like where it is desirable that the signage comprise illuminated letters or any other shapes that are easily seen, even at great distances, day or night. Each channel letter consists of an enclosure, usually a metal box, having a rear surface which is positioned against a raceway, or the wall of a building, on which the signage is mounted and a plurality of sides which define the figuration of a letter or number which make up a portion of the sign. A light source, such as a neon tube, is positioned within the walls of the enclosure and attached to the rear surface to provide illumination for the letter.
The light sources used in existing channel letters are neon bulbs requiring high voltage power with transformers built into the metal enclosures. To prevent injury to those servicing such channels letters many municipalities require that such letters be inspected to ensure that they are adequately sealed using standards set by Underwriters Laboratories.
It is expected that new technology will soon be available for the manufacturers of channel letters. Specifically, low voltage LED type light sources have been developed which provide a very long lasting bright light without requiring the high voltage and transformers needed for neon lighting. It is expected that channel letters employing the new technology will not be required to meet the standards set by Underwriters Laboratories.
In addition to the lighting, a channel letter also includes a planar, transparent lens, the outer shape of which corresponds to the figuration of the letter or any other shape defined by the sides of the enclosure. The lens of existing channel letters have a trim cap glued to the outer edges thereof which form a border to the lens. The trim cap also has a lip which, when assembled to the enclosure, is shaped to fit snugly around the forward ends of the walls thereof for retaining the lens to the enclosure and to maintain the water tight seal required by Underwriters Laboratories. Screws are threaded through the lips of the trim cap and into the walls to retain the lens across the forward opening of the enclosure.
The manufacture of the lens requires that a planar panel of transparent plastic be cut to the shape of the enclosure and that the trim cap be glued to the outer edges of the lens. The contours of the sides of many letters are curved and the process of shaping and gluing the trim cap around the edges of the lens is labor intensive. It is, therefore, expensive to manufacture existing lenses which fit across the forward ends of the enclosure of a channel letter.
It would be desirable to provide a channel letter having a lens which could be manufactured without incurring the labor intensive step of requiring the attachment of a trim cap. It would also be desirable to provide a less expensive method of manufacturing and assembling a lens to the enclosure of a channel letter.
Briefly, the present invention is embodied in a channel letter. For the purposes of this description, a channel letter is defined as including a letter of the alphabet, a numeral, an element of punctuation such as a comma, an exclamation point, or any other shape or form intended to constitute a portion of a sign.
The channel letter of the present invention has a rear surface for mounting against a raceway, a wall, or any other structure suitable for supporting the signage, and walls defining the figuration of the letter or shape to be depicted. A lighting element, such as a strip of LEDs according to the newly available technology or any other light source, is positioned against the rear surface of the enclosure to provide illumination therefore.
In accordance with one embodiment of the invention, to retain the lens to the open front of the enclosure, a shoulder is provided around the inner surface of the sides thereof where the shoulder defines a plane parallel to the outer ends of the sides but is recessed therefrom. A planar transparent lens having an outer edge which is in the shape of the letter and sized to fit within the sides of the enclosure is retained against the shoulder by retaining clamps or by screws extending through the walls of the enclosure with the distal ends thereof projecting in front of the lens.
Where the shoulder supporting the lens is made of rubber or foam, the shoulder may have insufficient rigidity to retain the lens against the elements. Over time, wind, rain, and ice may cause the rubber or foam to yield under the forces applied to the sign by the elements thereby allowing the lens to slide inward or rearward within the walls of the letter. The failure of the foam or rubber will cause the letter to have an unattractive appearance and can result in damage to the lighting fixture within the enclosures or damage to the lens and the wall of the letter. On the other hand, if the fasteners which retain the lens against the shoulder should fail, the lens may fall out of the enclosure altogether.
To prevent the failures described above, the invention may also have a first plurality and a second plurality of retainers spaced around the perimeter of the lens to provide support thereto. Each of the first plurality of retainers has a connector portion for connecting to the wall of the channel letter and a retaining portion which is positioned against the outer surface of the lens to retain it within the walls of the channel letter. Each of the second plurality of retains also has a connector portion and a retaining portion. The connecting portion attaches to the wall of the channel letter and the retaining portion provides support to the rear surface of the lens independent of the shoulder. The plurality of second retainers, therefore, prevents damage to the rubber, foam or other material which forms the shoulder.
In accordance with a second embodiment of the invention the foam or rubber strip around the inner surface of the letter described with respect to the first embodiment is deleted. In this embodiment the lens is again cut into the shape defined by the enclosure with dimensions that are a little less than the inner dimensions of the enclosure. The lens is held in place within the walls of the enclosure by a first plurality and a second plurality of retainers similar to those described with respect to the first embodiment. To provide a seal between the inner surface of the enclosure walls and the edge of the lens, a U-shaped rubber edging is fitted over the outer edge of the lens before the lens is fitted within the walls of the enclosure.
In accordance with a third embodiment of the invention, the lens is cut into the contour defined by the enclosure with the outer dimensions of the lens being a little larger than the outer dimensions of the enclosure such that the edges of the lens overhang beyond the outer edge of the enclosure. A rubber or foam stripping having a constant cross sectional shape is then glued to the inner surface of the enclosure with the forward surface of the rubber or foam projecting a short distance forward of the enclosure to form a seal against the rearward surface of the lens. A plurality of retainers around the perimeter of the lens attach the lens to the walls of the enclosure.